1. Field of the Invention
The present invention relates to small hand held motors and more particularly, to a hand held drill motor for use by dentists, surgeons, etc., and a control system therefor.
2. Description of the Prior Art
Drill motors for use by dentists and surgeons must be small enough to be carried in the doctor's hand. Such motors must have a variable speed and a high maximum speed capability. It is highly desirable that such motors also have the capability of stopping in a brief time interval to permit the quick substitution of drills or other tools. Sterilization of the motor as well as the drilling tools is also a requirement in many applications.
In the past, motors for use in dental and surgical drills have generally been of the pneumatic or electric d.c. (brush)type. Both the pneumatic and d.c. motors have variable speed capability with the pneumatic motors having a capability of a higher maximum speed than the d.c. motors. Pneumatic motors can be readily sterilized by autoclaving, that is, exposing the entire motors to a high temperature steam, for example, 150.degree. C. D.C. motors on the other hand are generally not designed to withstand autoclaving. Pneumatic motors must have a source of air or other fluid under pressure while d.c. motors can operate from the readily available source of alternating current with an appropriate power supply system. The prior art hand held motors do not have an independent speed and torque control.
Many problems inherent in the prior art hand held motors have been overcome by the present invention which provides a high torque, light weight variable speed motor which may be readily autoclaved. The speed and torque characteristics of the motor may be independently controlled over certain speed ranges and the motor may be stopped very quickly to permit the substitution of tools. The motor of the present invention has a long life and is also more highly resistant to the environment encountered in dentistry and surgical work.